This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This request for renewal of the PI's Lemieux account in the amount of 195,000 SUs, at the Pittsburgh Supercomputing Center(PSC), is based on two NIH supported research projects(one Program Project Grant(PPG) and one R01 Grants). The component of the PPG of which H. Weinstein is the PI is devoted to the structural context of the mechanistic study of neurotransmitter transporter(NT) function. The project investigates structural elements of NTs that determine and regulate their functions and their interaction with substrates, ligands and other cell components. The R01(Mehler, PI) has as its goal to gain new and deeper understanding of the Determinants of Function(DoF) of protein segments, which connect known elements of secondary structure, in the context of the complete molecular system. A specific aim of this project was the development, testing and application of a physically realistic loop structure algorithm and this has largely been completed. The PI's lemieux account for which renewal is being requested has been the main computational resource for this project and this support has made a major contribution to the achievements realized to date(see computational methodology and progress report, below) Both projects further build on continuing studies in the Weinstein and Mehler laboratories of the DoF of all components of transmembrane helices(TMHs).